The effect of lunar cycles
By DON MORROW
On Wednesday morning at St. Marks National Wildlife Refuge, moonset occurred at 2:43 a.m. This set in motion a number of related events.
First, it led to a high tide at the refuge later in the morning at 11:23 a.m. Tides are influenced by an interplay between the gravitational pulls of the moon, earth, and sun, as well as, the current orbital positions of the earth and moon. Tides are also affected by wind, barometric pressure, and water flow from adjacent uplands. This is complex stuff. Tides may also be affected by the direction of the stock market and the zodiacal house in which the moon is currently located, but tides are definitely affected by the moon.
Second, at 6:45 a.m. the rising Gulf tide hit the 2.5-foot level, at which the coastal mud flats along the refuge are inundated. This caused shorebirds to fly to the interior mudflats to wait until the tide dropped back below the 2.5-foot level in the early afternoon at 2:15 p.m. uncovering the coastal mudflats and allowing them to feed.
Third, because this represented optimal conditions for conducting a shorebird survey, my alarm was set for 4 a.m., allowing me to arrive at the refuge at 5:36 a.m. with enough time to drive out on the levees in the dark and be in position to start counting shorebirds just before sunrise at 7:14 a.m. While driving out, I heard King Rail and both Great Horned & Barred Owls. I flushed a Whip-poor-will off the levee and saw it fly away.
Although most of our summer-breeding shorebirds have left, shorebird numbers are increasing as migrants move through and wintering shorebirds begin to arrive. I logged 850 shorebirds of sixteen different species on the survey, starting with a flyover Whimbrel early in the morning.
I also found Pectoral, Western, Least, Stilt & Spotted Sandpipers; Black-bellied, Wilson’s & Semipalmated Plovers; Short-billed Dowitchers, an American Avocet, eleven Marbled Godwits, sixty-one Ruddy Turnstones, both Greater & Lesser Yellowlegs and one hundred and eighty-four Willets.
Most of the Black-bellied Plovers were molting out of breeding plumage, indicating that they had recently arrived from Baffin Bay, up in the high arctic of Canada. All the Willets seemed to be of the western subspecies that winters at St. Marks. Our breeding Willets, which winter along the South American coast, are gone. Other species, like the Spotted, Pectoral and Stilt Sandpipers, occur at the refuge only on migration. By next month, most of the transmigrants will have come through, but overall shorebird numbers will spike as wintering Dunlin begin to arrive.
It took me over five hours to complete the survey. Besides the shorebirds, there were Roseate Spoonbills, Reddish Egrets, and a huge flock of Black Skimmers. Yellow Warblers were common along the levee edges and I found my first Northern Harrier of the season. The first Bald Eagles return every August and on Wednesday, I found two nests already claimed by newly-returned eagles.
As with tides and shorebirds, my behavior is dictated by the lunar cycle. It is important to be in touch with the natural cycles of life. Come down to St. Marks and get connected. We’ll hook you up.
.
Don Morrow can be reached at donaldcmorrow@gmail.com.
